Multiple Sclerosis (MS) is the most common type of demyelinating disorder of the Central Nervous System (CNS) causing patches of sclerosis (plaques) in the brain and spinal cord that lead to a broad spectrum of neurological signs and symptoms. MS affects 400,000 Americans and 2.5 million individuals worldwide with an incidence of up to 20 new cases per 100,000 people per year in North America (Vollmer et al., 2007, Hader et al., 2007). MS typically presents in adults aged 20 to 45 years, but can occasional present in children and older patients. Two to three times more many women are affected than men.
The effect of MS progression is widely variable across patients. About 50% of patients reach the following disability milestones: loss of employment (10 years after diagnosis), need for assistive walking devices (15 years), and inability to walk (25 years). Additional impacts can include loss of arm function, loss of cognitive function, fatigue, weakness, pain, tremor, vision problems, urinary dysfunction, bowel dysfunction, muscle spasticity, swallowing disorders, sexual dysfunction, depression, anxiety, and others.
The heterogeneity of MS poses a challenge for the development of clinical guidelines, because very different types of clinical interventions may be needed for different patients. Neurologists have defined four main types of courses of MS. They are directly pertinent for clinical guidelines because therapies effective for one course are often not effective for others (Trisolini MG, AHRQ Expert Commentaries 2008).